1. Field of the Invention
The present invention relates to a position recognizing device and more particularly to a position recognizing device suited for assisting in precise mounting of IC component parts successively on a substrate by detecting a position of leads of each of the component parts.
2. Description of the Prior Art
A prior art position recognizing device used in an IC component mounting machine is designed so that an image of varying gradation obtained by viewing an IC component with a television camera is converted into image data which are subsequently stored in a storage unit and a template matching method is then applied to the image data to detect the position of two corners at tips of the leads, to thereby recognize the position of the leads.
In other words, as shown in FIGS. 5 and 6, a video signal carrying an image of an IC component 31 outputted from a television camera 32 is coinverted into binary image data by digitizing the video signal at a predetermined slice level using a digitizing means 33, and the binary image data are subsequently stored in an image storage unit 37. The image data so stored are sequentially transferred in response to instructions issued by a control unit 37 from the image storage unit 34 to a matching unit 35 in which a matching is carried out between templates 38a and 38b, outputted from a templet storage unit 36, with two corners at the tips of the leads of the IC component 31, which are carried by the image data, so that position information indicative of the point at which they match each other can be supplied to the control unit 37. In response to this position information supplied from the matching unit 35, the control unit 37 recognizes the position of the leads 39.
However, the foregoing system has been found suffer a drawback where the position of an IC component having leads extending outwardly in four directions is to be recognized using an image carried by rays of light reflected therefrom. Specifically, since the leads are so small in size as to result in bending thereof and the reflectance of light tends to vary depending on even a slight inclination of the IC component and the bending of the leads to such an extent as to vary the density of the image, the extent to which the digitized image data and the templet are matched with each other may be lowered, resulting in a difficulty in recognition of the position of the leads.
As a different position recognizing method, there is also known a method in which projection data of the image information are formed so that the run position and the run length at a predetermined slice level can be detected. Even this different position recognizing method suffers a drawback similar to that occurring in a pattern matching, particularly where the image density varies. Also, since the leads are generally of a shape in which, as shown in FIGS. 5 and 6, having respective portions intermediate of their length that are bent so as to represent a generally gull-wing shape, the projection data tend to considerably vary at positions corresponding to the bent portions of the leads and, therefore, it often occurs that the run and the lead do not match in shape with each other. Therefore, the different position recognizing method is not applied in practice for the position recognition of the leads.